precision validation of geant4 electromagnetic physics geant4 dna project meeting 26 july 2004, cern...
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Precision Validation of Geant4 Electromagnetic
Physics
Precision Validation of Geant4 Electromagnetic
Physics
Geant4 DNA Project Meeting
26 July 2004, CERN
http://www.ge.infn.it/geant4/analysis/test
Michela PiergentiliINFN Genova, Italy
S. Guatelli (INFN Genova), V. Ivanchenko (Budker), M. Maire (LAPP), A. Mantero (INFN Genova), B. Mascialino (INFN Genova), P. Nieminen (ESA), L. Pandola (INFN LNGS), S. Parlati (INFN LNGS), A.
Pfeiffer (CERN), M.G. Pia (INFN Genova), M. Piergentili (INFN Genova), L. Urban (Budapest)
Geant4 Electromagnetic
Physics
Geant4 Electromagnetic
Physics
Alternative models for the same physics processAlternative models for the same physics process
High energy modelsHigh energy models– fundamental for LHC experiments, cosmic ray experiments etc.
Low energy modelsLow energy models– fundamental for space and medical applications, neutrino
experiments, antimatter spectroscopy etc.
It handles electrons and positrons gamma, X-ray and optical
photons muons charged hadrons ionsmultiple scattering
Bremsstrahlung
ionisation
annihilation
photoelectric effect
Compton scattering
Rayleigh effect
gamma conversion
e+e- pair production
synchrotron radiation
transition radiation
Cherenkov
refraction
reflection
absorption
scintillation
fluorescence
Auger
Geant4 e.m. package
Standard Package
LowEnergy Package
Muon Package
Optical photon Package
Standard electromagnetic processesStandard electromagnetic processes
PhotonsPhotons– Compton scattering
conversion– photoelectric effect
Electrons and positronsElectrons and positrons– Bremsstrahlung– Ionisation
ray production– positron annihilation– synchrotron radiation
Charged hadronsCharged hadrons
Variety of modelsVariety of models for ionisation and energy loss
1 keV up to 100 TeV1 keV up to 100 TeV
Shower shapes
Courtesy of D. Wright (Babar)
Geant4 Low Energy Package Geant4 Low Energy Package
Geant4 Low Energy Package is fundamental for– Biomedical applications– Space Science– Neutrino and dark matter experiments
Geant4 Low Energy Package describes the interactions of photons, electrons, positrons, hadrons and ions with matter down to low energies.
Extensions of the physics models– down to 250 eV / 100 eV250 eV / 100 eV for electrons and photons– down to < 1 keV< 1 keV for protons, antiprotons, ions
Two models available: – based on evaluated data libraries – based on Penelope analytical models
Low energy Low energy e.m. e.m.
extensionsextensions
Low energy Low energy e.m. e.m.
extensionsextensions
Fundamental for neutrino/dark matter
experiments, space and medical applications,
antimatter spectroscopy etc.
e,down to 250 eV
0.01 0.1 1 100.01
0.1
1
10
100
1000
Geant4 LowEn NIST
/
(cm
2 /g
) in
iron
Photon Energy (MeV)
Based on EPDL97, EEDL and EADL evaluated data libraries
shell effects
Photon attenuation
Hadron and ion models based on Ziegler and ICRU data and parameterisations
Bragg peak
ions
antiprotons
protons
Processes à la PenelopeProcesses à la PenelopeThe whole physics content of the Penelope Monte Carlo code has been re-engineered into Geant4 (except for multiple scattering)
– for photons, electrons, positrons
Physics models by F. SalvatF. Salvat (University of Barcelona, Spain),
J.M. Fernandez-VareaJ.M. Fernandez-Varea (University of Barcelona, Spain), E. Acosta
(University of Cordoba, Argentina), J. SempauJ. Sempau (University of Catalonia, Spain)
Power of the OO technology:Power of the OO technology:– extending the software system
is easy– all processes obey to the same
abstract interfaces– using new implementations in
application code is simple
x-ray attenuation coeff in Al
Att
enuati
on c
oeff
. (c
m2/g
)
NIST data
Penelope
E.M. Physics Validation E.M. Physics Validation
Validation is fundamental in Geant4Validation is fundamental in Geant4
Validations at different levelsValidations at different levels
Comparisons to experimental measurements and Comparisons to experimental measurements and recognised standard referencesrecognised standard references
• Unit, integration, system testing• Microscopic physics validation• Macroscopic validation experimental use cases
Microscopic validationMicroscopic validation
Validation of Geant4 electromagnetic physics models
Attenuation coefficients, CSDA ranges, Stopping Power, distributions of physics quantities
Quantitative comparisons to experimental data and recognised standard references
G4Standard
G4 LowE
NIST
Photon mass attenuation coefficient
Photon mass attenuation coefficient
Photon beam (Io)
Transmitted photons (I)
0
ln1
I
I
d
2N-L=13.1 – =20 - p=0.87
2N-S=23.2 – =15 - p=0.08
x-ray attenuation coeff in U
NIST data
Penelope2=19.3
=22
p=0.63Absorber MaterialsAbsorber Materials:
Be, Al, Si, Ge, Fe, Cs, Au, Pb, U
Electron stopping power
and CSDA range Electron stopping power
and CSDA range G4 StandardG4 LowE-EPDL
NIST
CSDA range: particle range without energyloss fluctuations and multiple scattering
centre
Experimental set-up
Absorber MaterialsAbsorber Materials: Be, Al, Si, Ge, Fe, Cs, Au, Pb, U
2N-S=0.267 =28 p=1
2N-L=1.315 =28 p=1
G4 StandardG4 LowE-EPDL
NIST
Transmission tests
Transmission tests
e-
beam
Experimental set-up
Backscattering coefficient – E=100keV Backscattering coefficient – E=100keV
Angle of incidence (withrespect to the normal to the sample surface) = 0°
G4 LowE
Lockwood et al. (1981)
Incident e-
beam
Experimental set-up
Backscattered e-
The problem of validation: finding reliable dataThe problem of validation: finding reliable data
Note: Geant4 validation Note: Geant4 validation is not always easyis not always easy
experimental data often exhibit large differences!Backscattering low energies -
Au
ConclusionsConclusions
Geant4 electromagnetic package encompasses an ample set of physics models, specialised for particle type, energy range and detector applications
Exploitation of OO technology and sound architectural design make it possible to extend the Geant4 physics capabilities
– LowE / Livermore extensions– LowE / Penelope– LowE/ hadrons and ions
Geant4 e.m. physics is subject to a rigorous testing and validation process
Geant4 e.m. physics validation is in progress with Geant4 6.2 – IEEE TNS paper to be submitted in October
Geant4 Physics BookGeant4 Physics Book
A project has been launched for a Geant4 Physics Book
To have a solid and comprehensive reference on Geant4 physics
Wide effort involving Geant4 Collaboration
Main focus of the project is Geant4 physics models validation